The Revenge Of Jeff
by missakat
Summary: They've seen it all. Vampires, ghosts, demons; if you can name it, they've likely encountered it. But no experience could have prepared Sam and Dean Winchester for the oddities of Gravity Falls. And yet, for Mabel and Dipper, it's just another summer's day.


Their first summer in the mysterious town of Gravity Falls gave them a taste of adventure. Despite the increasing dangers, from the mystical creatures making residence in the depths of the landscape to the crazies who got their hands on ancient artifacts, they could not be kept away. The Pines parents had been surprised when the next summer, their children had pleaded to return to the wooded town. And to their great shock, the trend continued. While most teenagers would rather spend their summers hanging out, playing video games and letting the past school year's knowledge gradually melt from their minds, Mabel and Dipper Pines chose to return to the Mystery Shack.

The two of them remained close over the years, never losing their easy-going nature towards each other. Dipper worried incessantly about the looming figure of high school, but their transition into it went off without a hitch. Mabel found a group of friends who were only slightly less eccentric than she, much to Dipper's great happiness. High school had turned out to a decent experience. The one thing that both twin's friends found slightly strange was that the siblings were away each summer. While they were out in their Californian home, having fun and enjoying their two months of freedom, Dipper and Mabel politely declined their invitations, instead preferring to go to a rural town in the middle of the woods, boasting a minuscule population, and to the average teenager, nothing to do.

Dipper and Mabel had chosen not to tell anyone about their adventures in Gravity Falls. Sure, they told SOME stories, but they left out the more... supernatural parts. Like how Mabel's first boyfriend turned out to be a troupe of gnomes looking to marry her. Or that Dipper once fought a life-or-death battle with cursed wax figures out for Stan's blood. And the time that Mabel was possessed by grandparent-like ghosts in an abandoned convenience store. The list could go on and on. Enough books could be written to fill a library. Well, maybe not an entire library. A couple bookshelves at the least.

Their first summer in the quiet Oregon town was the strangest they had ever experienced. Not that the following years weren't even stranger, but they were more prepared for the mysteries and inevitable chaos. Dipper spent many a midnight hours poring over the pages of the journal he'd found, and with the added help of many internet sources, he was able to make additions to the already bountiful information. For their 14th birthday, after their second summer in Gravity Falls, Mabel had gotten Dipper his own journal. The leather bound notebook had since been filled with both diary-like entries giving his opinion on the situations they found themselves in, and pages of notes and observations of the various creatures they discovered in the woods.

And thus so, a couple hundred miles and a multitude of bus stops away from their home in Piedmont, the twins were once again at their Great Uncle's home. Dipper had just finished putting away all of his clothes when he heard the familiar shrill call of his twin from downstairs, "Dipper! Hurry UUUUP!"

"I'm coming! I'll just be a second!" Tucking his personal journal into his jacket, he hopped down the creaking steps. Despite the efforts of Soos, many aspects of the shack were in constant disrepair. While in some houses there was a single squeaky stair or floorboard, you would have to weigh next to nothing to traverse the shack's wooden floors without making a sound. Dipper landed with a thud on the worn carpet of the landing, and joined his twin sister in the kitchen.

Mabel was perched on one of the stools, swinging her legs impatiently as she waited for her brother. They had made plans to meet their co-workers and friends Wendy and Soos at the local diner that evening, and their appointed meeting time was quickly approaching. Mabel's normal attire still consisted of her decorated sweaters, which thankfully could no longer be found constantly attached to a hot glue gun, or some other sort of craft supply. Her thick brown hair was no longer just held back only a headband or a clip, but often put up in pony tails or crazy braids taught to her by her friends, from Gravity Falls and California alike. Luckily, she no longer needed braces, and thus had lost the slight lisp that was partnered with the metal attachments.

"Dipper, you're finally down." she complained, drawing out the words, "You're like a girl who spends hours doing her makeup just to go out!" The cheeky grin that spread across her face gave evidence to the taunt in her words.

"Oh shut up!" he protested. "I was putting my stuff away. Some of us don't just throw it onto the floor." his retort was paired with a grin practically identical to hers. She stuck her tongue out at him, and the two walked through the Mystery Shack's gift shop and out into the pine trees, following a trail they had traversed every summer for the past four years.

"Hey Sammy." Sam Winchester sucked in a deep breath, his brother's voice rousing him from sleep. He sat up in the leather seat, putting a hand to his eyes.

"Yeah Dean?"

The older Winchester, who was currently driving, turned his head to look at his slightly dazed sibling.

"There's a town coming up. You wanna stop in for the night?" He nodded at a sign that was coming up on the side of the highway, advertising one Gravity Falls coming up in a few more exits.

Sam, his head quickly clearing of any remnants of sleep, replied, "Yeah, might as well." The two of them were not currently on a job, and were driving aimlessly until a new case came up. Usually they would stick it out in a town for a few nights, but they had yet to find one that boasted a decent motel. This far from large populations, it was a bit difficult to find towns with citizens who were not immediately suspicious of outsiders.

Dean grunted as a reply, and not more than 10 minutes later they were turning down the twisted roads of Gravity Falls. Sam felt a quiet relief that the sun was still low in the sky, for he couldn't imagine how difficult it might be traversing the unkempt roads at night. The near-orange rays shone through the tall pines at varying intervals, highlighting the multiple pot-holes and cracks in the aged asphalt. A short trip lead to the local motel, a rustic complex almost hidden within the reddish trunks of the trees. They checked in, acquiring a room at the far end. The small lobby was filled with useless trinkets and advertisements, but Sam made sure to pick up an area map before joining Dean in the room.

"Gravity Falls..." he murmured aloud, while looking at the overly-touristy map. "I swear that I've heard that name before."

Dean snorted in response. "Well I certainly haven't." He stood up from where he had been splayed out on the bed. "Want to head into town? I saw a diner on the way in. And I'm in the mood for some pie. "

Sam smirked. "Sure. They might have a Wi-Fi connection too."

After packing away his laptop and a roll of bills, the brothers piled back into the Impala, and in a few minutes they were walking into the log shaped diner that had been dubbed "Greasy's Diner". They were immediately greeted with a draft of fried-food scented air, and headed in to one of the booths by the windows. The room was filled with what looked like locals, some of whom glanced up curiously at the new comers. Sam caught Dean's eyes scanning the room, assessing the potential threats, before lingering on the pretty red head sitting at the counter. Typical. She was sitting with a group of similarly haired boys, and an enormous man covered in ginger hair. Her family, obviously.

Shaking his head at Dean's antics, Sam pulled out his laptop and flipped it open. Remembering his feeling of slight familiarity with the town's name, he pulled open a search engine, for the possibility of finding more on the place. As he did so, their waitress came over. She had big hair, long fake nails, and one of her eyelids drooped to a closed position. She introduced herself as Lazy Susan, and asked what they would have. Dean ordered a slice of the cherry pie, while Sam politely declined the offer of food. He returned to his search, and a few minutes later Dean's order arrived. Sam pulled up the town's local newspaper, the Gravity Falls Gossiper. There was some information about the town, its origin and such, then recent newspaper articles. While still familiar, none of it gave enough of a push for him to remember where he'd seen the name.

Sam's face quirked into a slight frown, and he pulled out his phone. "I'm going to call Bobby."

Dean shrugged. "Go ahead," he stated, before returning to his pastry.

The phone rang, once, twice, three times, before a familiar gruff voice answered. "Sam?"

"Hey Bobby. Just a quick question. Have you ever heard of a place called Gravity Falls?"

From the other end of the line Sam could hear the older man shuffling papers around, before he replied. "Yeah, I've heard of the place. An old hunting buddy caught wind of something going on there, but when he got there, nothing was wrong. Kind of suspicious, but you can't go stopping trouble if there's nothing to be found. Why?"

A frown lit upon Sam's face, and he switched the phone to his other ear. "We're passing through the area and I recognized it, just couldn't remember from where. Thanks Bobby."

A small huff preceded Bobby's words. "Don't go getting yourself caught up in some mystery town. I'll let you know if there's any activity your way." With a quick goodbye, Sam hung up the phone and turned to Dean, whose attention was now divided between the dwindling amount of pie left on his plate, and the red head sitting at the counter.

Sam relayed the information to his brother, who shrugged. "Seems like a fluke." he said, closing the computer. Dean shrugged, his mouth clear of pasty for the current moment. "Not that that's a bad thing. We could do with a break. And this pie is awesome."

Sam rolled his eyes, and at that moment the diner bell dinged, announcing a new arrival.

**Author's Note: **

** Hello! Thank you for reading my fanfiction!**

** I'm planning on updating this every week or so, if my schedule (and attention span) allows for it. For the prevention of dropping this due to lack of inspiration, I wrote the whole of this story before I even considered posting it online. Updates will depend heavily on how quickly I am able to edit, as much of it has still been left untouched since the moments I first typed it into the keyboard. **

** I haven't seen many Supernatural/Gravity Falls crossovers, whether in drawing or writing form. This may simply be due to my not searching hard enough. I am not sure. Personally, I think that these two shows are perfect crossover material. I apologize for any out-of-character moments on the Supernatural front, I am not as immersed in that fandom. I find dialogue between characters very difficult, but I am trying my best to portray them correctly. **

** Just a note, I made Mabel and Dipper 16 in this fic for the sole purpose that Supernatural is more violent and gruesome than what most 12 year olds are regularly exposed to, even in a crazy town like Gravity Falls. **

**I hope you enjoyed! **

**~Missa**


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